Plenty to monitor with 49ers in preseason

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Newly signed receivers Austin Collie, right, and Lavelle Hawkins are among the 11 wideouts looking to earn a regular-season slot with the 49ers.

The NFL preseason is the biggest tease in pro sports.

It looks like football, sounds like football, but with very little on the line, it lacks the one ingredient that makes the NFL the most compelling game in the country: intensity. As a result, the preseason is only slightly more exciting than the Pro Bowl.

The 49ers open the 2013 preseason at Candlestick Park tonight against Peyton Manning and the Denver Broncos — an epic matchup if it was a regular-season game, potentially a Super Bowl preview. But Manning, the best quarterback of the last 15 years (perhaps), and Colin Kaepernick, the best quarterback of the next 15 years (perhaps), will only see the field for a couple of series at most, the equivalent of a pitcher throwing a bullpen session in between starts.

Jim Harbaugh won't show his hand, neither will John Fox. They're watching the third- and fourth-stringers, filling out their practice rosters.

Nevertheless, this year's preseason is filled with interesting subplots for the completely addicted fan. If you can't say no to football, here's a few things you can check out as you're counting down the seconds to the real season.

The education of Eric Reid: The 49ers' secondary is suddenly vulnerable with the departure of Dashon Goldson and the loss of Chris Culliver to a season-ending knee injury. Reid, the safety out of LSU the Niners took in the first round of the draft, should eventually be a Pro Bowl-caliber safety, but how long will take him to develop?

Craig Dahl will be the starting free safety against the Broncos, but Reid will see a lot of minutes throughout preseason and if he learns fast, he could be starting next to Donte Whitner later in the season.

Barrel of receivers: Every snap this preseason will be valuable to the 11 wide receivers hoping to find their way onto the field when the 49ers kick off the regular season against the Green Bay Packers on Sept. 8.

Last week, the 49ers signed Austin Collie and Lavelle Hawkins, adding more iron to the competition at receiver. With Kyle Williams, A.J. Jenkins, Kassim Osgood, rookie Quinton Patton, Ricardo Lockette, Marlon Moore, Chad Hall and undrafted rookie Chuck Jacobs already in the mix, it will be interesting to see who separates themselves from the pack.

The second coming: And we aren't talking about Kaepernick. Harbaugh is already comparing rookie tight end Vance McDonald to Hall of Famer Mike Ditka and he's bestowed him with his No. 89 to sport in red and gold this season.

Creative use of the tight end is a signature component of Harbaugh's offense and McDonald will step into a key role immediately replacing Delanie Walker in the double-tight end sets.

McDonald flew under the radar in college playing at Rice, so the preseason will be his first introduction to fans dying to catch a glimpse of his physical style of play.

Swiss army knife: Seventh-round pick B.J. Daniels could be the most exciting player on the 49ers' roster this preseason. The South Florida quarterback could see snaps from under center, in the backfield or out wide as a receiver. He's also expected to return punts and kicks.

If Daniels explodes this summer, he could be a wild card in Harbaugh's deck this season.

Paul Gackle is a contributor to The San Francisco Examiner. He can be reached at pgackle@sfexaminer.com and followed on Twitter @GackleReport.